This invention relates to an immersion oil formulation and more particularly to a low fluorescence immersion oil.
An immersion oil is used in microscopy and in other optical fields to fill some of the spaces in the optical system that would otherwise by filled with air or some other substance. The function of the immersion oil is to improve the quality of the light passing through the system.
In microscopy the primary use is to fill the gaps between a microscope oil immersion objective lens and the cover glass of the slide being viewed. The microscope and oil immersion objective are designed according to specified optical requirements for the immersion oil so that the image seen through the microscope will be of higher solution and brighter than is normally possible without the oil immersion system. In a similar manner optical coupling which may include the connection of optical fibers, lenses, flats and so on have similar requirements for immersion oils as those of the microscope manufacturers.
The most common optical requirements of an immersion oil for microscopy are a refractive index of 1.518 (5461 angstrom light) a dispersion value as expressed by a Abbe V of 44. Another common requirement is that the oil have low auto fluorescence. Prior to the ban of polychlorinated biphenyls (PCBs) by the U.S. Environmental Protection Agency, the vast majority of immersion oils were based on PCBs because of it desirable optical properties, stability and low auto fluorescence. Due to the ban, typical other types of immersion oils were formulated in an attempt to solve these problems.
See for example U.S. Pat. No. 3,929,667 issued on Dec. 30, 1975 to A Bautis and entitled IMMERSION OIL FORMULATIONS FOR USE IN MICROSCOPY AND SIMILAR FIELDS and assigned to the assignee herein. In any event, the reformulated immersion oils were inferior in some respects to their PCB counterparts particularly in regard to low auto fluorescence which is essential to fluorescent microscopy techniques. It is therefore an object of the present invention to provide a new and improved immersion oil possessing all the necessary optical characteristics of prior immersion oils while providing low fluorescence properties.